Determination of radium-228 in natural waters using extraction chromatographic resins
- Florida State Univ., Tallahassee, FL (United States)
- General Engineering Laboratories, Charleston, SC (United States)
We have developed a procedure for determination of {sup 228}Ra (t 1/2= 5.75 y) in natural waters using either the extraction chromatographic resins TRU-Spec{sup TM} or Ln-{center_dot}Spec{sup TM} to isolate the direct daughter, {sup 228}Ac, just before low-level counting. These separations are shown to be quantitative, simple, relatively fast, and free from most interferences. The recommended procedure effectively eliminates the need to perform the multiple precipitations and solvent extractions required by conventional techniques. The method uses a standard BaSO{sub 4} co-precipitation with {sup 133}Ba as an internal tracer to preconcentrate radium from a 1-2 L water sample. This is followed by a metathesizing process using K{sub 2}CO{sub 3} to convert the BaSO{sub 4} to the more soluble BaCO{sub 3} form. After the {sup 133}Ba yield determination, the sample (in HN0{sub 3}) is stored for {ge}30 hours to allow ingrowth of equilibrium amounts of {sup 228}Ac (t 1/2=6.14 h) from the {sup 228}Ra in the sample. This solution is then loaded onto a chromatographic column prerinsed with HN0{sub 3} followed by a rinse with sufficient HN0{sub 3} to completely flush out barium, radium, lead, and other common elements which may be contained in the sample load. Actinium is then eluted with either HCl or more concentrated HN0{sub 3} and is ready for low-level beta-particle counting after mounting by filtration or evaporation. We estimate a detection limit of {le}1.0 pCi/L in approximately 30 minutes of counting using a proportional counter with a 1.0 cpm total beta background, a {sup 133}Ba yield of 80%, and a 2-L sample volume.
- OSTI ID:
- 283322
- Journal Information:
- Radioactivity and Radiochemistry, Vol. 6, Issue 3; Other Information: PBD: 1995
- Country of Publication:
- United States
- Language:
- English
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